The present invention relates to an appliance end fitting for connecting a pressurized gas cylinder with a gas appliance such as a barbecue grill wherein the end fitting incorporates an improved and simplified construction that incorporates a dual function flow control and thermal shutoff valve.
Gas appliances such as barbecue grills are connected to pressurized propane or LP gas cylinders by means of an appliance end fitting on the end of an appliance supply hose or pressure regulator that is connected to an outlet valve on the gas cylinder. Standardized outlet valves are employed for gas cylinders, and appliance end fittings are designed to be compatible with these standardized outlets.
A gas cylinder assembly includes a gas cylinder and an outlet fitting. Cylinder outlet fittings usually incorporate a number of safety features, including a pressure relief valve, a manual shutoff valve operated by a hand wheel, and an automatic shutoff located inside an annular collar forming an outlet for the cylinder assembly. Such automatic shutoff valves usually include a valve member that is biased outwardly to a normally closed position against a valve seat, with the valve member being resiliently openable by inward pressure thereon to permit gas to flow from the cylinder.
An early standardized coupling or end fitting for connecting a gas appliance to a gas cylinder is called a POL coupling. In a POL coupling, an elongated tubular body having a rounded nose or nipple on an inner end fits inside the annular outlet collar of the cylinder assembly and is attached thereto by a left handed pipe thread connection between the outer surface of the body and the inner periphery of the collar, with the body being attachable by a wrench. The body is threaded into the outlet until the nipple opens the automatic shutoff valve, at which time the nipple sealingly engages a valve seat in the outlet and constrains gas flow from the outlet to a longitudinal opening through the elongated body. The outer end of the body typically is threaded externally so as to mate with a standardized nut or threaded opening on a hose or pressure regulator leading directly or indirectly to the gas appliance.
A newer style of standardized coupling is a so-called QCC-1 or Type 1 coupling. In such a coupling, the outlet collar of the cylinder assembly includes an external right hand acme thread, and the appliance end fitting that couples the cylinder to a pressure regulator or hose leading to the gas grill includes a large, hand-operable nut rotatably mounted on an elongated body of the type used in a POL coupling. Engagement of an internal acme thread on the nut with the external acme thread on the cylinder assembly outlet axially slides the body into the inlet, where the nipple on the end (still sometimes referred to as a POL type nipple) engages and opens the automatic shutoff valve in the cylinder assembly outlet. A Type 1 end fitting also generally includes another safety feature, a thermal shutoff valve that automatically shuts off the supply of gas from the gas cylinder in the presence of excessive heat that may be indicative of a flame traveling up the fuel line to the cylinder tank. There are a number of types of devices that do this. One type of device causes the ejection of the appliance end fitting from the cylinder itself in the presence of excess heat, thus actuating the cylinder outlet automatic shutoff valve. Other devices cause an internal shutoff valve in the coupling to actuate in the presence of excess heat. These valves generally operate by plastic parts that melt or soldered connections that melt in order to permit a biased valve member to close.
Appliance end fittings also sometimes include excess flow control valves, which automatically restrict or shut off the flow of gas from the tank when the rate of flow of gas is excessive. This can occur when a fuel line is cut, for example, in order to prevent excess fuel from escaping. Excess flow control valves and thermal shutoff valves typically are separate valves.
In a newer valve construction, an additional safety feature is incorporated into the cylinder assembly. This is a so-called overfill protection device (OPD). This is a valve that fits inside the LP tank and automatically shuts off a tank filling operation when the tank becomes filled to the desired level. Propane or LP fuel is provided in liquid form and requires a certain amount of open space in the cylinder, so that the fuel can be provided in vaporized form through the cylinder outlet. An example of an overfill prevention valve is shown in U.S. Pat. No. 5,842,500.
In all three of the most common standardized cylinder valve assemblies, a POL fitting, a Type 1 fitting, and an OPD fitting, a standardized coupling device or appliance end fitting is required. The device can be threaded on or it can employ a so-called quick connect fitting of various designs. An object of the present invention is to provide an improved appliance end fitting for a standardized connection wherein a single valve member operates as an excess flow control valve as well as a thermal shutoff valve in an economical construction.